Variable-stroke car shifting apparatus

ABSTRACT

A car shifting apparatus for moving cars of different lengths includes axle-engaging dogs and a sensor mechanism actuated by a car wheel for controlling the respective engagements and disengagements of the dogs with the appropriate axles of the cars. Telescopic fluid pressure motors serve to advance and to retract the dogs through strokes which are dependent upon the distances between successive trucks of the cars as reflected by the action of the sensor mechanism.

United States Patent Anderson et a].

[ 51 Oct. 10, 1972 VARIABLE-STROKE CAR SHIFIING APPARATUS Inventors: Charles M. Anderson; Edward H.

Ratcliff, Jr., both of Paris, Ky.

Assignee: W. R. Stamler Corporation, Paris,

Filed: Dec. 29, 1969 Appl. No.: 888,597

US. Cl ..104/162, 104/173 Int. Cl. ..B61j 3/08 Field of Search ..104/162, 176; 91/173 References Cited UNITED STATES PATENTS 9/1968 Saxonmeyer ..104/176 2,572,687 10/l95l Anderson et a1. ..214/42 3,377,961 4/1968 l-lunt ..104/162 Primary Examiner-James B. Marbert Assistant Examiner-Robert Saifer Attorney-William E. Sherwood ABS I'RACT A car shifting apparatus for moving cars of different lengths includes axle-engaging dogs and a sensor mechanism actuated by a car wheel for controlling the respective engagements and disengagements of the dogs with the appropriate axles of the cars. Telescopic fluid pressure motors serve to advance and to retract the dogs through strokes which are dependent upon the distances between successive trucks of the cars as reflected by the action of the sensor mechanism.

10 Claims, 9 Drawing Figures PATENTEBUU 10 :972

SHEET 2 [IF 6 INVENTORS CHARLES M. ANDERSON EDWARD H. RATCLIFF, JR.

BY /4/ Swat-T74 ATTORNEY PATENTEDncI 10 I972 sum 3 BF 6 INVENTORS CHARLES M. AN DERSON EDWARD H. RATCLIFF, JR.

ATTORNEY PATENTEDnm 10 I972 saw u or 6 INVENTORS CHARLES M. ANDERSON EDWARD H. RATCLIFF, JR.

I ATTORNEY PATENTEDnm m I972 3.6 96. T54

' SHEET 5 BF 6 BY M ATTORNEY PATENTEDBBT 10 I912 3.696. 754

SHEET 5 UF 6 INVENTORS CHARLES M. ANDERSON EDWARD H. RATCLIFF, JR.

ATTORNEY VARIABLE-STROKE CAR SHIFTING APPARATUS BACKGROUND OF THE INVENTION Various industrial uses of railway cars which are to be loaded or unloaded at a fixed station require that the locomotive be detached from the trip of cars and that such trip of cars be advanced by a car shifting apparatus. In some instances, the cars are equipped with special members, such as car-hauls, adapted for engagement with the dogs of the shifting apparatus and in other instances the dogs are arranged to engage with some integral portion of the car itself, such as the lower surface of the trucks mounting the axles and wheels of the cars. The car shifting apparatus conventionally includes a pair of elongated fluid motors, each of which has a piston rod carrying one or more slides or barneys upon which the dog or dogs are pivotally mounted. The respective directions of simultaneous travel of these piston rods are controlled in accordance with the positions occupied by the dogs of the respective piston rods and by the positions occupied by those portions of the cars which are engageable with the dogs at a given moment.

This conventional apparatus works satisfactorily when each of the cars is of the same length, but when a trip of cars includes cars of different lengths or with different heights of, or differently shaped, trucks, various problems arise. For example, when a long car is followed in the trip by a shorter car, an excessive length of retracting travel of the dogs may ensue with a resulting heavy impact of the dog and car when the following advancing travel occurs.

Various suggestions for employing a stroke selector for overcoming this problem have been advanced, but as far as we are aware, such suggestions have required a complicated and relatively expensive mechanism. When a separate compensating cylinder is included in the hydraulic system to provide a variable stroke of the pistons; or when the variable stroke is achieved by an arrangement as disclosed in Hunt US. Pat. No. 3,377,961, or when a system employing travelling control switches is used, such equipment generally is substantially more complex than that of the present invention. Furthermore, when the car shifting apparatus is to be mounted between the rails of the track, as in the present invention, a requirement for a compact assembly exists and this in turn imposes column-strength restrictions on the size of the piston rod employed, as when a single piston rod for a motor is long enough to have a stroke equal to one-half of the distance between the trucks of the longest car to be used in the trip of cars.

It is these and other disadvantages found in the conventional forms of car shifting apparatus which it is a purpose of our invention to overcome.

SUMMARY The car shifting apparatus of the present invention includes a pair of parallel-positioned fluid pressure motors which are single acting and each of which comprises a stationary cylinder with a hollow piston rod extending to and cooperating with a movable cylinder, and with a barney-carrying solid piston rod extending from the movable cylinder. The barney includes a pivoted dog biased to a normal car axle-engaging position and the respective barneys are interconnected so that as one of the motors is undergoing a telescoping action, the companion motor will be undergoing an extending action.

One of the barneys carries a sensing means at its forward end and which is actuated by the leading wheel of the following truck of the car as the sensing means is retracted during the telescoping of its corresponding motor. A simple hydraulic system includes a main control valve for determining the supply of pressure fluid to and exhaust from the respective motors and the shifting of this valve is controlled by a simple electrical circuit in which only three switches are required. One of these switches is actuated by the sensing means associated with one of the motors and the other two switches are respectively actuated as the other of the motors reaches the established limits of its extended and telescoped movements.

Among the objects of the invention is the provision of a simple and compact variable-stroke car shifting apparatus; the provision of a car shifting apparatus engageablewith the axles of cars and actuated by a car wheel to determine the length of the next successive stroke of car advancement; the provision of an improved sensing means for establishing the length of stroke of a variable-stroke car shifting apparatus; and the provision of an improved and simplified electrically controlled hydraulic system for use with the car shifting apparatus.

These and other objects and advantages of the invention will become more apparent as the description proceeds and when considered in conjunction with the accompanying drawings in which:

FIG. 1 is a plan view of the forward end of the apparatus with portions broken away.

FIG. 1A is a plan view of the rear end of the apparatus, complementary to FIG. 1, and with portions broken away.

FIG. 2 is a view to a larger scale taken on line 2-2 of each of FIGS. 1 and 1A and indicating the compact relation of the apparatus to the rails, and with the sensing means being shown in its normal position.

FIG. 3 is a side elevation view, with parts broken away, of the right-hand telescopic fluid pressure motor with the barney attached thereto having its dog in pushing position with respect to a car axle.

FIG. 4 is a plan view of the sensing means to a large scale.

FIG. 4A is a rear elevation view of portions of the sensing means similar to that seen in FIG. 2, but with the car wheel in engagement therewith.

FIG. 4B is an end view of portions of the sensing means as taken on line 4B-4B of FIG. 4 and extended to indicate the mounting of the control valve.

FIG. 5 is a diagrammatic view of the simplified hydraulic system and its associated electrical control indicating the position of the apparatus at the time of transfer from the left-hand dog to the right-hand dog, and

FIG. 6 is a schematic view indicating the spatial relation of the sensing means to the dog of the barney upon which the sensing means is mounted.

Referring now to FIGS. 1 and 1A, a supporting framework which is positioned between the track rails 10, 11 includes a forward end member 12 and a rear end member 13 with parallel side guides 14,15 and a center guide 16 rigidly attached to and extending between the end members. Rigidly mounted between guides 14 and 16 is a stationary single-acting cylinder 17, herein called the right-hand cylinder in accordance with :the direction of movement of the cars, and having a fluid connection 18 at its'rear end. A similar stationary cylinder 19 having a fluid connection 20 at its rear end is mounted between guides and 16 and is suitably displaced longitudinally from cylinder 17.

As best seen in FIG. 3, the right-hand motor includes a hollow piston rod 21 attached at one end to a hollow piston 22 disposed in cylinder 17 and attached at a ball joint 23 at its outerend to the rear end 24 of a movable cylinder 25. Disposed within cylinder 25 is a solid piston 26 having a solid piston rod 27 projecting from the forward end of that cylinder. The distal end of this solid rod is connected with a ball joint 28 to the rear end of the right-hand barney 29, later to be described. As indicated in FIGS. 1 and 2, the barney includes four pivoted shoes 30 to 33 at its sides, and the movable cylinder 41, a solid piston rod 42 and a pivoted-shoeequipped barney 43. Moreover, the barneys of the respective motorsare coupled by means of a cable 44 attached at its ends to the barneys and passing around a sheave 45 rotatably mounted on the stationary framework. The pivoted shoes of the left-hand motor engage with ribs 46,47 on the confronting faces of guides 15 and 16, as seen in FIG. 2.

As will be understood, one of the motors, here shown as the right-hand motor, is located parallel to and in advance of its companion motor and when either of the motors is caused to extend to its full stroke, the other motor is caused to telescope upon itself by the action of the cable 44. Accordingly, if, for example, a maximum stroke of 40 feet is provided for each motor and which would be suitable for long cars having an 80-foot length between trucks, it is possible to employ -foot lengths for the stationary and movable cylinders of each motor and with cylinder diameters substantially less than the diameter of a cylinder which would have a 40-foot piston rod requiring a large rod diameter suitable for appropriate column strength. With the present arrangement of telescoping motors, the overall height of the motors between the rails, as seen in FIG. 2, is such as to enable the user to install them substantially level with the tops of the rails. I

Referring now to FIG. 3, the barney 29, which is essentially similar to the barney 43 except for the sensing means attached to the latter, comprises a rigid box-like construction having side walls 51,52, a rear wall 53 and a front wall 54. A heavy boss 55 affixed to the rear wall includesa concave seat for the ball joint end of the solid piston rod 27 and an abutment 56 fixed within the barney provides a concave seat against which the convex end of the dog now to be described is adapted to bear. This dog includes an elongated member 60 having a bell crank arm 61 attached thereto and with the member 60 pivotally mounted upon a pin 62 extending transversely of the barney. A tension spring 63 connected to the arm 61 and anchored upon an abutment 64 within the barney serves to hold the dog normally in elevated position. A depending arm 65 pivotally mounted on the member 60 and having a lost-motion slot 66 at its lower end. engageable with a pin 67 mounted within the barney serves to'limit the height to which the dog may be raised. One or more depending sleeves 68 rigidly attached to member 60 and adapted to slide along the inner walls of the barney serves to prevent side sway of the dog during its movement between retracted and extended positions.

At its forward end, the member 60 includes a support 70 for a pair of spaced rollers 71,72 which are adapted to contact and to rotate with the trailing axle 73 of the truck of the car being pushed by the dog. A shield 74 extending rearwardly from support and overlying a portion of member 60 acts to cam the dog downwardly against the action of spring 63 when such shield encounters a part of a car during the retracting movement of the barney.

Referring now to FIGS. 1 and 1A, an end stroke limit switch adapted to be actuated by a portion of barney 29 as the right-hand motor reaches the forward limit of its maximum stroke is mounted upon the guide 14 at a fixed location. Similarly, a mid-stroke limit'switch 81 adapted to be actuated by a portion of the barney 29 as the right-hand motor reaches the rearward limit of. its stroke, is mounted upon the guide 14 at a fixed location. As a feature of the invention, an elongated vane 82 is mounted upon the outer surface of guide 15 and pivotally suspended from brackets 83,84 for swinging movement transversely of the guidev 15 and of the track rail 11, as best shown in FIG. 2. A variable stroke-control switch 85 is adapted to be suitably actuated by the vane when the vane is moved by the sensing means now to be described. As shown in FIG. 4 the sensing means includes a carriage body generally indicated at 86 and attached by means of a clevis 87 to the front wall 54 of the left-hand barney. Pivoted shoes 88,89 at the sides of the carriage body ride upon the same ribs 46, 47 as do the shoes of the barney 43 and the associated movable cylinder 41 of the left-hand motor. Laterally projecting from the top, of the body 86 above the shoe 88 and over the guide 15 is a rigid cantilever arm 90 upon which a movable cam-supporting framework is pivotally mounted by a pin 91 extending through the arm 90. This framework includes parallel side arms 92,93 joined by a cross brace 94 at the distal ends and with a suitable cam 95, preferably a roller journalled in the brace 94, being supported thereon for the purpose later to appear.

Intermediate the ends of the side arms. a depending bracket is rigidly affixed to these arms and includes side strips 96,97 joined at their bottom ends by a floor 98 extending rearwardly toward fixed guide 15, as best.

shown in FIG. 4B. Supported beneath the floor plate 98 is another cam 99, preferably a roller journalled in the floor plate and which is adapted to engage the vane 82 when the framework is pivoted to the position indicated in FIG. 4A.,A tension spring 100 anchored at one end upon the distal end of projection 90 and at the other end upon the floor plate 98 serves to bias the framework normally into the position seen in FIG. 2 at which cam 95 occupies a position in which it will contact the flange 101 of a car wheel W. A rigid bar 102 extending across strips 96,97 beneath the arm 90 serves to limit the upward movement of the pivoted framework.

As will be apparent, the roller 95 travels in the space alongside the ball portion of rail 1 1, which space is constantly being cleared of cinders, ice or other obstruction as the wheels of the cars move along the rail. When depressed by the flange 101 of a wheel, the framework of the sensing mechanism pivots downwardly bringing the roller 99 into contact with the elongated vane 82 provided that the sensing means is not in advance of the leading edge 103 of that vane (FIG. 1). Significantly, the vane, which preferably includes an upper rod 104 journalled in brackets 83,84 on the undersurface of the top flange of guide (FIG. 2), is so positioned lengthwise of the structure that when the left-hand motor reaches its forwardmost position, the sensing means will have been pushed sufficiently far beyond edge 103 of the vane so that upon beginning of the next retracting movement of that left-hand motor the two wheels of the truck which that motor had been pushing will idly depress the sensing framework twice before the vane can be next actuated. Thus, the setting of the control valve 112 remains unchanged and the left-hand motor can continue its rearward movement until the leading wheel of the next successive truck is encountered and at which time the movement of the sensing framework will cause its roller 99 to push against the vane 82.

As shown, the vane 82 normally hangs in a vertical plane and a pin 105 fixed to guide 15 (FIG. 2) and projecting through a hole in the vane with a biasing spring 106 surrounding the pin serves to hold the vane normally in contact with the head of pin 105 and to limit inwardly swinging movement of the vane when the vane is engaged by roller 99. The open space between the vane and the guide 15 allows drainage of water and the dropping downwardly of cinders or the like so that malfunctioning in the environment in which the apparatus is used will be obviated.

Referring now to FIGS. 1, 1A and 6, the mid-stroke switch 81 for the right-hand motor is so positioned that the dog of the barney of that motor will be about 6 inches rearwardly of the axle with which the dog of the barney of the left-hand motor is engaged when the movements of the motors is to be reversed following the maximum forward stroke of that left-hand motor. At this time and as indicated in FIG. 6, the spacer 108 which dictates the distance between the sensing mechanism and the elevated position of the dog carried by the left-hand barney is serving to hold the roller 95 in advance of the leading wheel of the truck, here shown as the leading truck of the car. As will be understood,.the roller 95 at this time is in advance of the forward end 103 of the vane by a distance greater than one-half of the distance between the two axles of that truck.

i In association with the above-described apparatus, a simplified hydraulic system as shown in FIG. 5 is employed. A conventional pump 110 driven by any suitable motor draws fluid from reservoir 111 and directs the same to a conventional control valve 112. This valve may conveniently be a spring-offset, solenoidcontrolled, pilot-operated, directional valve such as the Vickers type DG 5S4-lO2A-T-50, having a spring 113 normally holding the valve in position to supply fluid to conduit 18 leading to stationary cylinder 17 and to vent fluid from stationary cylinder 19 through conduit 20. When the coil 114 is energized the valve then shifts to reverse these flows. Moreover, the invention makes possible the use of a simplified electrical circuit for operating valve 112 including a conventional relay having contacts 116 connected to lines L, and L, and which contacts are adapted to close and remain closed when the latch coil 117 is appropriately energized momentarily. Conversely, these contacts are adapted to open and remain open when the release coil 118 is appropriately energized momentarily. Conventional switch contacts 119, 120 and 121 associated respectively with the end stroke limit switch 80, with the midstroke limit switch 81, and with the variable stroke control switch are incorporated in the electrical circuit and function in the manner now to be described.

OPERATION OF THE CAR SI-IIFTING APPARATUS Assuming that a trip of cars, including cars of different lengths between their leading and trailing trucks, have been moved to operating position on the apparatus shown in FIGS. 1 and 1A, and with the righthand fluid motor fully telescoped and with the dog of barney 29 located a few inches behind the trailing axle of the leading truck of the forwardmost car of the trip; the valve 112 (FIG. 5) will then be positioned as follows to supply fluid to the right-hand motor to cause its advancement and to vent fluid from the left-hand motor to cause its telescoping retraction. At this moment, the dog of barney 43 (FIG. 6) is in contact with the described axle, but is ready to begin its retracting movement and the dog on barney 29 is in readiness to engage that axle. The mid-stroke switch 81 at this moment is closed and since its switch contacts also are closed momentarily a circuit is made from L, through conductor 122, switch contacts 120, conductor 123 and the coil 118 to line L Temporary energization of release coil 118 opens contacts 116 until the next energization of the latch coil 117 with the result that the former circuit from L, through contacts 116, conductor 124, solenoid 114 and to line L, is now broken. At this time valve 112 will occupy the position shown in FIG. 5 under the bias of spring 113.

Fluid entering cylinder 17, hollow piston rod 21, and movable cylinder 25 of the right-hand motor causes the barney 29 and its dog in engagement with the axle to move forwardly, and the cable 44 causes the barney 43 and its sensing means to move rearwardly. This movement opens switch 81 and the switch contacts of 120 but the relay contacts 116 remain open.

The right-hand motor then moves forwardly for its entire maximum stroke and simultaneously the dog of the left-hand motor is brought into elevated position behind the trailing axle of the trailing truck of the car being so moved. If the car length is commensurate with the maximum stroke, the switch 80 will be closed by the right-hand motor at the same time the vane 82 is being moved by the sensing means on the left-hand motor to close switch 85. Thus, the closing of switch contacts 119 or 121 by the first to occur of these events causes a circuit to be made either from L through contacts 119, conductor 125, latch coil 117 and thence to L,, or from L through conductor 126, contacts 121, conductor 127, latch coil 117, and thence to L,.

The temporary energization of latch coil 117 closes the then open contacts 116 and causes energization of solenoid 114, whereupon valve 112 is shifted against the bias of spring 113. At this time fluid passes into cylinder 19, hollow piston rod 40, and movable cylinder 41 causing the dog on barney 43 to push against the trailing axle of the trailing truck of the same car. The cable 44 now causes the right-hand motor to move rearwardly until the switch 81 again is closed and the release coil 118 is again temporarily energized to effect shifting of valve 1 12.

When, however, after a movement of. less than its maximum stroke the left-hand motor again moves rearwardly, the sensing means will be operated by the leading wheel of the leading truck of the next succeeding carin the trip and will close the switch contacts 121 before the right-hand motor makes its maximum stroke sufficient to operate the end stroke limit switch 80 as above described.

Immediately upon the closing of switch 85 by the sensing means, the latch coil 117 is energized, contacts 116 close, solenoid 114 is energized and the forward movement of. the right-hand motor is interrupted. At this time, fluid is then supplied to the left-hand motor and the dog of barney 43 pushing upon the trailing axle of the. leading truck of the second car in the trip will make its less than maximum forward stroke and which stroke is terminated when the rearwardly moving righthand motor again closes switch 81.

As will be understood, this same operation of the sensing means would have occurred had the first car of the trip been of a length insufficient to permit the righthand motor to have operated the switch 80 before that sensing means became operative. Accordingly, the apparatus is suited for handling not only cars-of different lengths, but alsov for handling trips of cars in which the coupling spaces between adjacent cars may be widely varied. At the conclusion of the final pushing operation in a trip of cars,.the apparatus may be inactivated merely by de-energizing the motor which drives the pump, or by other suitable action. Although the invention is particularly suited for use with cars having two axles per truck, it may be employed also with :cars having a single axle per truck merely by shortening the spacer 108 between the sensing means and the barney 43.

The use of the telescoping motor construction permits not only the employment of small diameter cylinders and the subdivision of the motors into shorter cylinders and piston rods for ease in handling for shipment or storage, but also makes possible the use of a single barney anddog assembly for each motor and a reduced number of reversals of the fluid flow while shifting a car of a given length as compared with the use of multiple barney-dog assemblies for each motor. Moreover, the use of a rolling contact between the dog and the axle being pushed provides practical advantages not available when the dog is required to engage the truck body or a car-haul specially provided for dog engagement.

Having thus disclosed a preferred form of variablestroke car shifting apparatus, it will be understood that the invention may be embodied in other forms than that described as being the preferred form.

What is claimed is:

1. In an apparatus for shifting a trip of cars, a pair of fluid pressure motors, first and second barneys carried.

respectively by said motors and having means for engaging a car to be pushed thereby, a fluid pressure system connected to said motors and including a control valve for supplying and for venting fluid to and from said motors; each of said motors including a stationary cylinder having a hollow piston rod projecting therefrom, a movable cylinder attached to said hollow rod and receiving fluid therefrom, and a second piston rod movable within said movable cylinder and attached to the barney carried by the motor;'a cable connected to said barneys and adapted to telescope one of said motors when the other of said motors is being extended, and a sensing means carried by said first barney for shifting the position of said control valve during retracting movement of said sensing means thereby to reverse the directions of movement of said motors, said sensing means being actuated by contact with a car being shifted by said apparatus.

2. Apparatus as defined in claim .1 wherein said means for engaging the car comprises a movable dog pivotally mounted on the barney and biased into a raised car axle engaging position.

3. Apparatus as defined in claim 2 wherein said dog is movable into axle engagement independently of movement of said sensing means.

4. In an apparatus for shifting a trip of cars, a pair of fluid pressure motors, first and second barneys carried respectively by said motors and adapted to be reciprocated simultaneously in opposite directions through a maximum length of stroke, each of said motors including a stationary cylinder having a hollow piston rod projecting therefrom, a movable cylinder attached to said hollow rod and receiving fluid therefrom, and a second piston rod movable within said movable cylinder and attached-to the barney carriedby the motor, a cable connected to said barneys and adapted to telescope one of said motors when the other of said motors is being extended, said barneys having means for engaging the axle of a car to be pushed thereby, a fluid pressure system connected to said motors and including a control valve for supplying and for venting fluid to and from said motors, and a laterallyprojecting wheel-engaging sensing means carried by said first barney and projecting into the path of movement of the car wheel, said sensing means being adapted upon contacting the car wheel to shift the position of said control valve during the retracting stroke of said first motor whereby the next following advancing 5. Apparatus as defined in claim 4 wherein said sensing means is disposed forwardly of said car-engaging means carried by said first barney by a distance greater than the distance between the axles of the truck of the car.

6. Apparatus as defined in claim 5 wherein said sensing means includes a cam engageable by the flange of the car wheel and said car engaging means includes a roller adapted for rolling contact with the car axle.

7. Apparatus for shifting a trip of cars comprising a pair of fluid pressure motors disposed between the car rails, first and second barneys carried respectively by said motors and adapted to reciprocate simultaneously in opposite directions, said barneys having means for engaging the car axles and for moving the car thereby by pushing upon the axle when the corresponding barney is moving in an advancing direction and its corresponding motor is being extended, each of said motors including a stationary cylinder having a hollow piston rod projecting therefrom, a moveable cylinder attached to said hollow rod and receiving fluid therefrom and a second piston rod movable within said movable cylinder and attached to the barney carried by the motor, a cable connected to said barneys and adapted to telescope one of said motors when the other of said motors is being extended, a fluid pressure system connected to said motors and including a solenoid operated control valve for supplying and for venting fluid to and from the motors, a laterally-projecting wheel-engaging sensing means carried by said first barney and projecting into the path of movement of the car wheel, and an electrical circuit for controlling the setting of said valve and including the solenoid of said valve, first and second switches adapted to be actuated respectively when said second barney reaches the forward and rearward limits of its maximum stroke, and a third switch adapted to be actuated by said sensing means during the rearward movement of said first barney and upon contact of said sensing means with the car wheel. I 8. Apparatus as defined in claim 7 including an elongated member mounted adjacent the rail on which the car wheel travels and rockable between a normal first position disconnected from said third switch and a second position actuating said third switch, said sensing means being adapted to travel along the elongated member and to rock the same into said second position upon engagement of the sensing means with the car wheel.

9. Apparatus as defined in claim 8 wherein said sensing means includes a body member attached to and disposed in advance of said first barney and slideable parallel to said rail, a transversely extending upwardly biased framework pivotally mounted on said body, a first cam mounted on said framework in position to be engaged by the flanges of a car wheel travelling on said rail, and a second cam mounted on said framework and movable along the side of said member, said second cam being adapted to contact and to move said member to its second position when said framework is pivoted downwardly.

10. Apparatus as defined in claim 9 wherein said first and said second cams comprise rollers. 

1. In an apparatus for shifting a trip of cars, a pair of fluid pressure motors, first and second barneys carried respectively by said motors and having means for engaging a car to be pushed thereby, a fluid pressure system connected to said motors and including a control valve for supplying and for venting fluid to and from said motors; each of said motors including a stationary cylinder having a hollow piston rod projecting therefrom, a movable cylinder attached to said hollow rod and receiving fluid therefrom, and a second piston rod movable within said movable cylinder and attached to the barney carried by the motor; a cable connected to said barneys and adapted to telescope one of said motors when the other of said motors is being extended, and a sensing means carried by said first barney for shifting the position of said control valve during retracting movement of said sensing means thereby to reverse the directions of movement of said motors, said sensing means being actuated by contact with a car being shifted by said apparatus.
 2. Apparatus as defined in claim 1 wherein said means for engaging the car comprises a movable dog pivotally mounted on the barney and biased into a raised car axle engaging position.
 3. Apparatus as defined in claim 2 wherein said dog is movable into axle engagement independently of movement of said sensing means.
 4. In an apparatus for shifting a trip of cars, a pair of fluid pressure motors, first and second barneys carried respectively by said motors and adapted to be reciprocated simultaneously in opposite directions through a maximum length of stroke, each of said motors including a stationary cylinder having a hollow piston rod projecting therefrom, a movable cylinder attached to said hollow rod and receiving fluid therefrom, and a second piston rod movable within said movable cylinder and attached to the barney carried by the motor, a cable connected to said barneys and adapted to telescope one of said motors when the other of said motors is being extended, said barneys having means for engaging the axle of a car to be pushed thereby, a fluid pressure system connected to said motors and including a control valve for supplying and for venting fluid to and from said motors, and a laterally-projecting wheel-engaging sensing means carried by said first barney and projecting into the path of movement of the car wheel, said sensing means being adapted upon contacting the car wheel to shift the position of said control valve during the retracting stroke of said first motor whereby the next following advancing stroke of said first barney after actuation of said sensing means will be of a length less than the maximum stroke whenever the distance between the leading wheels of adjacent car trucks of the trip is less than twice the length of said maximum stroke.
 5. Apparatus as defined in claim 4 wherein said sensing means is disposed forwardly of said car-engaging means carried by said first barney by a distance greater than the distance between the axles of the truck of the car.
 6. Apparatus as defined in claim 5 wherein said sensing means includes a cam engageable by the flange of the car wheel and said car engaging means includes a roller adapted for rolling contact with the car axle.
 7. Apparatus for shifting a trip of cars comprising a pair of fluid pressure motors disposed between the car rails, first and second barneys carried respectively by said motors and adapted to rEciprocate simultaneously in opposite directions, said barneys having means for engaging the car axles and for moving the car thereby by pushing upon the axle when the corresponding barney is moving in an advancing direction and its corresponding motor is being extended, each of said motors including a stationary cylinder having a hollow piston rod projecting therefrom, a moveable cylinder attached to said hollow rod and receiving fluid therefrom and a second piston rod movable within said movable cylinder and attached to the barney carried by the motor, a cable connected to said barneys and adapted to telescope one of said motors when the other of said motors is being extended, a fluid pressure system connected to said motors and including a solenoid operated control valve for supplying and for venting fluid to and from the motors, a laterally-projecting wheel-engaging sensing means carried by said first barney and projecting into the path of movement of the car wheel, and an electrical circuit for controlling the setting of said valve and including the solenoid of said valve, first and second switches adapted to be actuated respectively when said second barney reaches the forward and rearward limits of its maximum stroke, and a third switch adapted to be actuated by said sensing means during the rearward movement of said first barney and upon contact of said sensing means with the car wheel.
 8. Apparatus as defined in claim 7 including an elongated member mounted adjacent the rail on which the car wheel travels and rockable between a normal first position disconnected from said third switch and a second position actuating said third switch, said sensing means being adapted to travel along the elongated member and to rock the same into said second position upon engagement of the sensing means with the car wheel.
 9. Apparatus as defined in claim 8 wherein said sensing means includes a body member attached to and disposed in advance of said first barney and slideable parallel to said rail, a transversely extending upwardly biased framework pivotally mounted on said body, a first cam mounted on said framework in position to be engaged by the flanges of a car wheel travelling on said rail, and a second cam mounted on said framework and movable along the side of said member, said second cam being adapted to contact and to move said member to its second position when said framework is pivoted downwardly.
 10. Apparatus as defined in claim 9 wherein said first and said second cams comprise rollers. 